Curtain for electrolytic cells



0ct120, 1931. L. E. WARD 1,328,006

' CURTAIN FOR ELECTROLYTIC CELLS Filed July 29, 1929 2 Sheets-Sheet l wy I V h; LL.

INVENTOR ATTORNEY Oct. 20, 1931. L. E. WARD CURTAIN FOR ELECTROLYTICCELLS Filed July 29, 1929 2 Sheets-Sheet 2 F1 .5 F135 Fig.7

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INVENTOR BY mam/W4 ATTORNEY Patented Oct. 20, 1931 NITED STATES PATENTDFF-ICE LOUIS E. WARD, OF MIDLAND, MICHIGAN, ASSIGNOR TO THE DOWCHEMICAL COM- PANY, OF MIDLAND, MICHIGAN, A CORPORATION OF MICHIGANCURTAIN FOR ELECTROLYTIC CELLS Application filed July 29,

This invention relates in general to a curtain-like means for separatinganodic from cathodic products of electrolysis. It relates specificallyto a sectional type of curtain adapted for use in separating metallicmagnesium and chlorine gas produced by the electrolysis of a fusedsaline bath containing magnesium chloride.

Owing to the high temperature to which such a curtain is exposed, thecorrosive action of chlorine and other anodic products and further tothe fluxing 0r erosive action of the fluid hot metal upon ceramic warein general, and still further to the necessity that the ourtain haveelectrical non-conductive property, the choice of material for such acurtain is somewhat narrow and the details of construction requirecareful design. Refractory material such as fire-clay or brick shapes iscustomarily employed and because such material suffers erosion,corrosion, or breakage it is essential that the details of design shallper.- mit the easy substitution of new parts to replace those no longerserviceable. -It may be stated, in general, that such pieces of largesize are relatively more expensive than those of small size, are moredifficult to pack, ship, unpack, and store without breakage and are morereadily broken when handled in a replacement operation. Small pieces, onthe contrary, are more cheaply made, more easily packed and transported,easily stored in small space, and can be handled with a minimum ofbreakage and loss.

I have invented a curtain composed of a plurality of suitably shapedplates of simple design and small size and have invented further meansto construct same and means to support said plates in the cellpermitting the easy removal and replacement of any single piece evenwithout suspending operation of the cell during such repairs.

To'the accomplishment of the foregoing and related ends, the invention,then, consists of the means hereinafter fully described and particularlypointed out in the claims, the annexed drawings and the followingdescription setting forth in detail certain means for carrying out theinvention, such disclosed means illustrating, however, but several of1929. Serial No. 381,795.

various ways in which the principle of the invention may be used.

In said annexed drawings Fig. 1 is a vertical transverse section of anelectrolytic cell employing my invention and adapted to the electrolysisof a fused saline bath for the separation of a metal which will floatthereon. Fig. 2 is a vertical longitudinal section through said cell andFig. 8 is a plan thereof with the cover plates removed to show myimproved curtain and other details. Fig. 4 is a side elevation and Fig.5 an edge View of a member of the curtain shown in Figs. 1, 2, and 3.The Figs. 6 and 7 are edge views of modified forms of such curtainmember.

Referring to Figs. 1, 2, and '3, showing a type of cell to which myimproved curtain is adapted, 1 is a cathode pot set in a furnace adaptedto supply initial or control heat for the bath. A sin le anode or aplurality 2 depend in the bat from above and are preferably set in astraight line between opposing cathode surfaces of the pot. furtherpreferably supported by adjustable hangers permitting motion in avertical direction, removal of anodes from the bath, reinsertion thereinand for adjusting the depth of dipping in the bath.

In the type of cell illustrated, the pot is provided with an invertedtrough 3, adapted to trap liberated metal rising through the bath fromthe principal cathode surface 4 of the pot. Such metal is shown at 5 inthe cross hatched areas. The bath level will be approximately as shownin Figs. 1 and 2. Provision may be advisedly made to lead the lightmetal so entrapped to a collecting well or gathering zone permittingeasy access for removing theso collected metal. Such a collecting wellis shown at 15 and the metal collected therein at 17. A second well 6,shown beside well 15 in the plan view Fig. 3, is separated from thelatter by the partition 7 and affords access to the cell for theinsertion of a dipper .or like utensil by means of which sediment or socalled sludge may be dredged from the bath while the cell is inoperation. The metal collecting in the well 15 may likewise be dipped orotherwise removed from The anodes are the cell without interruptingoperations. One side 3 of the inverted trough adjacent the collectingwell 15 is removed to enable the metal entrapped therein to float outinto the collecting well. The removed side is shown in dotted lines as3' in Fig. 2, which dotted lines may be also taken to represent theunremoved portion thereof adjacent the well 6.

The curtain separating the anodic from the cathodicbath areas ispreferably composed of an assembly of refractory plate-like membershaving surface projections or other equivalent contours enabling thesupport thereof upon the cell superstructure. Such a curtain isillustrated in longitudinal cross section in Fig. 2 in plan in Fig. 3,and in transverse section in Fig. 1.

My curtain, prepared in accordance with the present invention, will beseen to consist of a number of refractory plate-like curtain members 18having a hook-like projection adapted to engage with a correspondingprojection upon the trap 3 upon which or from which said curtainmembershang in close juxtaposition to form a rectangular enclosure aboutthe anodes. The construction of the individual curtain members, as shownin assembly thereof in Figs. 1, 2, and 3, is clearly shown in Figs. 4and 5, which latter figures present a side and edge view, respectively,of

said separate or individual curtain member,

in which the hookslike projection is shown at 19. A variation in design18 of such curtain member is shown in Fig. 6 and a still furthervariation thereof 18" in Fig. 7, the variation in Fig. 6 having respectto the projecting portion 20 and that in Fig. 7 to the absence of suchprojecting portion. The so projecting portion 20 is intended to addheight to the curtain when desirable and affords an opportunity toinsert therein openings or other variation in contour adaptedto engage atool for handling the curtain member. Each member of the curtainassembly is supported independently of the others and is separatelyplaceable therein and removable therefrom, a distinctive feature beingthe manner of support which is accomplished by providing, as staed, ahook-shaped projection, engaging with a complementary projection alongthe upper edge of the collecting trough 3.

T he curtain assembly 'so formed of a plurality of separate removableplate-like members not only serves as a refractory curtain separatinganodic from cathodic portions of the bath, but blankets also theotherwise active surface of the trough 3, restricting cathodic actionthereon, and the consequent liberation of metal not normally collectiblein the trap. The curtain members may be constructed of a varietyofmaterials among which are fire-clay or fire-brick materials,- sintcredmagnesia, ceramic ware, such as porcelain and the like, resistant to thebath at the temperature employed.

Various modifications in the form of the curtain members may be employedwithout departing from the spirit of my invention and such variationswill be evident to one skilled in the art.

WVhen in the course of operation of an electrolytic cell employing acurtain of the type herein disclosed, should one or more members of theassembly become eroded, broken, or otherwise'unfit for further serviceit may be readily replaced with a new member without interrupting theoperation of the cell. To do this I provide in a convenient locationsuch new member heated to the approximate temperature of the bath. Ithen remove 'one or more of the cover plates 8, which inclose the anodicgas space IO-above the bath, giving access to the member to be removed.Sufficient suction will be carried upon the gas duct 11, connectedthrough the a similar tool pick up and lower into place the new curtainmember, after adjusting which, I then replace the covers. During theoperation just described the cell may be continued in operation withoutloss of output.

My invention is applicable to advantageous use in both large and smallscale operation It isparticularly applicable in large scale operationsemploying a plurality of anodes in a large cell. A sectional curtain forsuch a cell may be readily constructed of small pieces or plates of thecharacter described to form a rectangular, oval, circular, or otherenclosure or partition for leading the anodic gas to the outlet, forcovering exv posed portions of the pot upon which it is desired torestrict cathodic action, and for separating the floating metal from theanodic products. Such a curtain may be constructed far more cheaply andsafely than a large sized single piece curtain and renewals will beconfined to the replacement of small pieces for any one breakage whereaswhen large single piece curtains are used, breakage at a single pointwill require the substitution of a new piece of large size and cost. Notonly are small refractory pieces more cheaply made than large ones butthey suffer less breakage in drying, burning, packing, shipping, andstorage. They require less boxing and packing materials for shipment,less storage room and less labor in handling, are in many respectshighly advantageous relative to large sized pieces. I have found thedisadvantage incident to the discontinuous character of the curtain, dueto the more or less imperfect joint obtainable in actual practicebetween the adjoining plate edges, to

present no serious difiiculties in operation. It is customary to employa suction upon the anodic gas chamber of the cell which effectuallyprevents issue of the chlorine through the joints in the curtain, andsuch joints are sufficiently close in practice to substantially preventmetal from passing into the anodic compartment from without. In the formof cell construction illustrated in Fig. 1, the bulk of the metalliberated is trapped as indicated, and but a small portion is liberatedupon the surfaces of the metal adjacent to the curtain to become laterliable to passage in part through the curtain joints into the anodic gaschamber before removal as metal product.

Other modes of applying the principle of my invention may be employedinste d of the one explained, change being made as regards the mechanismherein disclosed,--provided the means stated by any of the followingclaims or the equivalent of such stated means be employed.

I therefore particularly point out and distinctly claim as myinvention 1. In apparatus of the character described, the combination ofa cathode pot, an invertedtrough-like trap along the upper limit of theprincipal cathode surface thereof, a projecting rim along the, upperside of said trap, and a curtain assembly including a plate-likenonconducting hook-shaped member engaging with said rim as supporttherefor.

2. In apparatus of the character described, the combination of a cathodepot, an inverted trough-like trap along the upper limit of the principalcathode surface thereof, a projecting rim along. the upper side of'saidtrap and a curtain assembly composed of a plurality of hook-shapedplate-like non-conducting members engaging with said rim as supporttherefor. I r

3. In apparatus for electrolyzin a fused salt bath, a plate-like curtainmem er of re-. fractory material having a hook-like projecs tion adaptedto engage with a support so as to be suspended vertically therefrom, andcapable of being assembled edge to edge with other like members 'to forma continuous sectional partition wall or curtain. 7

4. In apparatus for electrolyzing a fused salt bath, a sectionalpartition of refracto material to separate anode and cathode pro uctscomprising a pluralityof generally plate-shaped members each having ahooklike projection engaging a support so as to be suspended verticallytherefrom edge to ed e with companion members to form a lateralIybounded enclosure.

5. In apparatus for electrolyzing a fused salt bath, the combination ofa vessel to contain such bath and forming the cathode, anodesdependingin said bath and a sectional partition of refractory material toseparate anode and cathode products comprising a plurality of generallyplate-shaped members each having a hook-like projection engaging I asupport therefor so as to be suspended vertically edge to edge withcompamon members to form an enclosure circumscribing said anodesanddipping below the surface of said bath.-

6. In apparatus for electrolyzing a fused salt bath, the combination ofa vessel to contain such bath and forming the cathode, an invertedtrough-like flange around the inner 'wall of said vessel adapted toentrap metal rising from the cathode surface and floating on said bath,an upwardly projecting run along the inner edge of said flange, anodesdepending in said bath'and a sectional partition of refractory materialto separate anode and cathode products comprising a plurality ofgenerally plate-shaped members each having a hook-like projectionengaging said rim so as to be suspended vertically therefrom edge toedge with companion members to form an enclosure circumscribing saidanodes and dipping below the surface of said bath.

Signed by me this 25 day of July, 1929.

. 'LOUIS E. WARD.

